Studies of the mechanism of induction of SV40 virus from non-virus producing virogenic hamster kidney cells transformed by SV40 are being carried out. In particular, the mechanism of induction by mitomycin C and amino acid deprivation are being studied. We are analyzing the number of viral genomes per cell, whether the viral DNA is excised from the chromosome of the transformed cell, and the species of RNA transcribed after induction. Various clones of virogenic hamster kidney cells have been isolated which differ in their inducibility. Some clones yield virus spontaneously, while others can be induced only after mitomycin C treatment; other clones are not inducible at all. the reasons for this observed heterogeneity are also being examined. Studies of the cancer cell membrane are being continued. In particular, sulfated acid mucopolysaccharides and hyaluronic acid metabolism in normal and transformed cells and their roles in masking the lectin agglutinable sites in normal cells are being determined. In addition, the role of proteases in causing the transformed cell phenotype is being examined, as well as the effect of anti-protease compounds in restoration of the normal cell phenotype and contact inhibition to the transformed cell.